1. Field of the Invention
This invention is directed to a method and apparatus for treating strand-like material, and more particularly for heat setting such material to provide for the shape retention of the material.
2. Description of the Prior Art
An example of the above-mentioned material shape retention is the ability of a heatset textile carpet yarn to resist crushing by springing back to shape when walked upon for a much longer time than a non-heatset carpet yarn. To obtain this kind of advantage, the heat setting of the material may take place in apparatus of the type generally described in U.S. Pat. No. 3,683,650, issued Aug. 15, 1972. In the operation of such apparatus, the strand-like material such as yarn is laid in loops in a type of spiral coil about conveyor means in the form of a plurality of narrow conveyor belts or ropes arranged at corners of the loops to transport the loops downstream to a heating zone. While in U.S. Pat. No. 3,683,650 apparatus is provided to rotate the coil carrying conveyor ropes while in the heating zone, it has been found that this is not necessary in all instances and in fact, in the description and examples set forth herein, the conveyor ropes were not rotated. While in the heating zone wherein the coil material is heat set, it has been found that due to the contact between the loops and the ropes as the loop material shrinks during the heat setting thereof, certain damage or non-uniform conditioning has been caused to the loop material such that in a subsquent dyeing operation irregularities occur. In particular, when the loop material has been heat set as described above and manufactured into a carpet during a tufting operation and is then dyed using conventional dyeing equipment, upon visual observation a pattern of light flecks are perceived on the surface of the dyed carpet in a scattered pattern. In a piece of carpet dyed brown, for example, the flecks appeared beige in color and are so numerous as to be unacceptable to the customer. Thus, a method and apparatus for overcoming this problem is desired.